Bump actions/upload-artifact from 4 to 6 (#156)

Bumps [actions/upload-artifact](https://github.com/actions/upload-artifact) from 4 to 6.
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](actions/upload-artifact@v4...v6)

---
updated-dependencies:
- dependency-name: actions/upload-artifact
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/windows_build_test_and_push.yml

@@ -66,7 +66,7 @@ jobs:
           .\7z.exe a $Env:GITHUB_WORKSPACE\ImperatorToCK2-win-x64.zip $Env:GITHUB_WORKSPACE\Release\*
           cp $Env:GITHUB_WORKSPACE\ImperatorToCK2-win-x64.zip $Env:GITHUB_WORKSPACE\ImperatorToCK2-latest.zip
 
-      - uses: actions/upload-artifact@v4
+      - uses: actions/upload-artifact@v6
         if: ${{ github.event_name != 'push' }}
         with:
           path: Release/
@@ -143,7 +143,7 @@ jobs:
           fronter_dir: 'Fronter.NET'
           release_dir: 'Release'
 
-      - uses: actions/upload-artifact@v4
+      - uses: actions/upload-artifact@v6
         if: ${{ github.event_name != 'push' }}
         with:
           path: Release/